Effect of relative humidity on the thin-layer chromatographic separation of E 472 emulsifiers

E 472 emulsifiers are organic acid esters of mono- and diacylglycerides. These emulsifiers are categorized into six subgroups (E 472a-f) based on the specific acid component, e.g., acetic acid, lactic acid, citric acid, tartaric acid, or mixtures of tartaric and acetic acid. The present study investigated the effect of relative humidity (RH) on the thin-layer chromatographic separation of four E 472 emulsifier subgroups, addressing practical concerns due to RH variations between seasons and within laboratories. Three RH-setting techniques affecting plate activity and chamber climate were assessed using saturated salt and aqueous sulfuric acid solutions. Aqueous sulfuric acid solutions for RH adjustment resulted in decreased hRF values, while no trends in hRF value changes were observed for saturated salt solutions. Unlike RH itself, the RH setting technique led to substantial changes in the chromatographic fingerprint. Thus, the choice of the RH setting method should be tailored to the specific analyte and analysis goal. Despite variations in chromatographic fingerprints between the three RH setting techniques, the fingerprint remained consistent within the same technique across the tested RH range.